Although understanding has improved hugely amongst clients as to what they require in the files I supply them there are still many who do not seem to understand some of the terms or processes they are referring to when asking me to supply photo files.
Here are some of the questions I have had in the last couple of months that have made me realise some clients/designers either assume I know what THEY are doing or THEY don't know what they are doing...
a) The jpeg you sent is 1mb, I need a 5mb file
b) It needs to be big enough for X by Y cm
c) I need the RAW file
d) can you convert the file to CMYK for us, when we converted it it didn't come out right.
So first thing is file size which should answer questions like a and b.
Let's define a few terms
My cameras record 4,288 x 2,848 pixel images. (4,288 x 2,848 = 12,212,224 pixels or 12.3mp)
Different image uses require a different number of pixels or dots per inch. Typical examples are computer screens (web) which uses 72 ppi, newspapers which are 200-250 dpi, high end magazines are typically 300-330 dpi and billboards may be only 15 dpi or as little as 2 dpi. So you can see that my files of 4,288 x 2,848 could produce a web page 60 inches x 40 inches or a magazine image 14 inches x 9 inches or a billboard of 23 feet by 15 feet with no alteration of the file pixel dimensions.
I supply most of my clients with jpeg files produced by exporting a version of the processed RAW file from photoshop lightroom.
This jpeg file is produced by taking the original file and putting it through an algorithm that looks at ways to reproduce the image in a manageable file size by applying a user specified trade off between quality and file size.
Part of this algorithm represents large areas of the same colour using far less information than requiring the file to allocate the same colour value to several thousand individual pixels. This wastes space.
The upshot of this is that detail requires more information and thus larger jpegs result.
In simple terms, a photo of a piece of white paper would result in a far smaller jpeg than one from a photo of a newspaper page taken with the same camera.
So question a) shows me the designer hasn't opened up the file and looked at the quality and dimensions to see if it works for their layout because they don't understand what a Jpeg really is.
Question b) requires the missing variable of dpi. ie I need the image to be 20 x 15 cm @ 300dpi.
Of course often I send the full size file, all 4,288 x 2,848 pixels of it and it is still not enough for the use the client has in mind. I get back a request like "Our designer needs a bigger file than you supplied" This is often after I have already explained this is the file in the dimensions produced by the camera. So the designer knows the image needs to be extrapolated up in size. My question is what sort of designer doesn't have photoshop and doesn't know how to enlarge an image using 'Image Size'?
A RAW file contains all the information the camera recorded about the colours the camera saw when I pressed the shutter. That is 12 bits of information per pixel. When I see the image in Lightroom I may tweek the colours (temperature, tint, exposure) based on experience and because I was there when the photo was taken so I know what it should look like or what I want it to look like. It is also likely I have made other alterations to the image. I may have cropped the shot, straightened the horizon and removed dust spots. These alterations would be lost if I gave the client the RAW file as it came from the camera. It is called RAW because that is what it is... the raw material the image is made from. Not the finished product.
The Red Green Blue (RGB) colour space is used by computers and other types of screens to view images. Cyan, Magenta, Yellow and Key (black)(CMYK) is the colour space used by printing presses to put ink on paper. Different print presses and paper combinations require different specific pofiles to convert an RGB file to a CMYK file that will be used by the press to put the correct amount of ink on to the paper type specified by the client.
This isn't a generic "convert to CMYK" process some think it is. The conversion should either be done by the printer or by the designer using a profile supplied by the printer.